Surprising Symbolic Model Formula Evaluations

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Surprising Symbolic Model Formula Evaluations

Emi Tanaka
Hi,

I'm wondering about some logics behind the following simplifications:

y ~ 1:x simplifies to y ~ 1
y ~ x:1 simplifies to y ~ 1
y ~ x*1 simplifies to y ~ x
y ~ 1*x simplifies to y ~ 1

Mainly I would have expected y ~ 1:x to simplify to y ~ x and the cross
operator to be invariant to order.

I have some further surprising cases below that I'd also like to know more
about but just above will also be great.

https://rpubs.com/emitanaka/unexpected-formula-eval

Best,

Emi

*Dr. Emi Tanaka* | Lecturer in Statistics

Faculty of Science, School of Mathematics and Statistics


Secretary, NSW Branch, Statistical Society of Australia
<https://www.meetup.com/NSW-Branch-of-the-Statistics-Society-of-Australia/>

Social Media Coordinator, Central, International Biometrics Society
<https://twitter.com/IBSstats>


*THE UNIVERSITY OF SYDNEY*
827, Carslaw F07 | The University of Sydney | NSW | 2006
*Phone:* +61 2 9351 3039
*Website:* * <http://sydney.edu.au/>*https://emitanaka.github.io/
*Twitter: *@statsgen

CRICOS 00026A
This email plus any attachments to it are confidential.
Any unauthorised use is strictly prohibited. If you receive this email in
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Re: Surprising Symbolic Model Formula Evaluations

Richard M. Heiberger
I can't duplicate your examples
This is what I see
> y ~ 1:x
y ~ 1:x

Please try again in a vanilla R session, and send a reproducible example.
vanilla means start R from the operating system command line with
R --vanilla

this prevents any of your initialization files from being loaded.  See
?Startup
for details.

On Fri, Oct 11, 2019 at 1:05 PM Emi Tanaka <[hidden email]> wrote:

>
> Hi,
>
> I'm wondering about some logics behind the following simplifications:
>
> y ~ 1:x simplifies to y ~ 1
> y ~ x:1 simplifies to y ~ 1
> y ~ x*1 simplifies to y ~ x
> y ~ 1*x simplifies to y ~ 1
>
> Mainly I would have expected y ~ 1:x to simplify to y ~ x and the cross
> operator to be invariant to order.
>
> I have some further surprising cases below that I'd also like to know more
> about but just above will also be great.
>
> https://rpubs.com/emitanaka/unexpected-formula-eval
>
> Best,
>
> Emi
>
> *Dr. Emi Tanaka* | Lecturer in Statistics
>
> Faculty of Science, School of Mathematics and Statistics
>
>
> Secretary, NSW Branch, Statistical Society of Australia
> <https://www.meetup.com/NSW-Branch-of-the-Statistics-Society-of-Australia/>
>
> Social Media Coordinator, Central, International Biometrics Society
> <https://twitter.com/IBSstats>
>
>
> *THE UNIVERSITY OF SYDNEY*
> 827, Carslaw F07 | The University of Sydney | NSW | 2006
> *Phone:* +61 2 9351 3039
> *Website:* * <http://sydney.edu.au/>*https://emitanaka.github.io/
> *Twitter: *@statsgen
>
> CRICOS 00026A
> This email plus any attachments to it are confidential.
> Any unauthorised use is strictly prohibited. If you receive this email in
> error, please delete it and any attachments. Please think of our
> environment and only print this e-mail if necessary.
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> [hidden email] mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

______________________________________________
[hidden email] mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
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Re: Surprising Symbolic Model Formula Evaluations

Bert Gunter-2
Rich:

> x <- 1:10
> y <- runif(10)
> lm(y ~ 1:x)

Call:
lm(formula = y ~ 1:x)

Coefficients:
(Intercept)
      0.477

> lm(y ~ x:1)

Call:
lm(formula = y ~ x:1)

Coefficients:
(Intercept)
      0.477

> lm(y ~ 1*x)

Call:
lm(formula = y ~ 1 * x)

Coefficients:
(Intercept)
      0.477

> lm(y ~ x*1)

Call:
lm(formula = y ~ x * 1)

Coefficients:
(Intercept)            x
   0.493927    -0.003079

Cheers,
Bert


Bert Gunter

"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Fri, Oct 11, 2019 at 10:59 AM Richard M. Heiberger <[hidden email]>
wrote:

> I can't duplicate your examples
> This is what I see
> > y ~ 1:x
> y ~ 1:x
>
> Please try again in a vanilla R session, and send a reproducible example.
> vanilla means start R from the operating system command line with
> R --vanilla
>
> this prevents any of your initialization files from being loaded.  See
> ?Startup
> for details.
>
> On Fri, Oct 11, 2019 at 1:05 PM Emi Tanaka <[hidden email]>
> wrote:
> >
> > Hi,
> >
> > I'm wondering about some logics behind the following simplifications:
> >
> > y ~ 1:x simplifies to y ~ 1
> > y ~ x:1 simplifies to y ~ 1
> > y ~ x*1 simplifies to y ~ x
> > y ~ 1*x simplifies to y ~ 1
> >
> > Mainly I would have expected y ~ 1:x to simplify to y ~ x and the cross
> > operator to be invariant to order.
> >
> > I have some further surprising cases below that I'd also like to know
> more
> > about but just above will also be great.
> >
> > https://rpubs.com/emitanaka/unexpected-formula-eval
> >
> > Best,
> >
> > Emi
> >
> > *Dr. Emi Tanaka* | Lecturer in Statistics
> >
> > Faculty of Science, School of Mathematics and Statistics
> >
> >
> > Secretary, NSW Branch, Statistical Society of Australia
> > <
> https://www.meetup.com/NSW-Branch-of-the-Statistics-Society-of-Australia/>
> >
> > Social Media Coordinator, Central, International Biometrics Society
> > <https://twitter.com/IBSstats>
> >
> >
> > *THE UNIVERSITY OF SYDNEY*
> > 827, Carslaw F07 | The University of Sydney | NSW | 2006
> > *Phone:* +61 2 9351 3039
> > *Website:* * <http://sydney.edu.au/>*https://emitanaka.github.io/
> > *Twitter: *@statsgen
> >
> > CRICOS 00026A
> > This email plus any attachments to it are confidential.
> > Any unauthorised use is strictly prohibited. If you receive this email in
> > error, please delete it and any attachments. Please think of our
> > environment and only print this e-mail if necessary.
> >
> >         [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > [hidden email] mailing list -- To UNSUBSCRIBE and more, see
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
>
> ______________________________________________
> [hidden email] mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

        [[alternative HTML version deleted]]

______________________________________________
[hidden email] mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
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Re: Surprising Symbolic Model Formula Evaluations

R help mailing list-2
In reply to this post by Richard M. Heiberger
Look at what terms() (hence lm()) does with such formulae:
> str(terms(y~1*x))
Classes 'terms', 'formula'  language y ~ 1 * x
  ..- attr(*, "variables")= language list(y, x)
  ..- attr(*, "factors")= int(0)
  ..- attr(*, "term.labels")= chr(0)
  ..- attr(*, "order")= int(0)
  ..- attr(*, "intercept")= int 1
  ..- attr(*, "response")= int 1
  ..- attr(*, ".Environment")=<environment: R_GlobalEnv>
> coef(lm(y~1*x, data=data.frame(y=1:10,x=log2(1:10))))
(Intercept)
        5.5


Bill Dunlap
TIBCO Software
wdunlap tibco.com


On Fri, Oct 11, 2019 at 10:59 AM Richard M. Heiberger <[hidden email]>
wrote:

> I can't duplicate your examples
> This is what I see
> > y ~ 1:x
> y ~ 1:x
>
> Please try again in a vanilla R session, and send a reproducible example.
> vanilla means start R from the operating system command line with
> R --vanilla
>
> this prevents any of your initialization files from being loaded.  See
> ?Startup
> for details.
>
> On Fri, Oct 11, 2019 at 1:05 PM Emi Tanaka <[hidden email]>
> wrote:
> >
> > Hi,
> >
> > I'm wondering about some logics behind the following simplifications:
> >
> > y ~ 1:x simplifies to y ~ 1
> > y ~ x:1 simplifies to y ~ 1
> > y ~ x*1 simplifies to y ~ x
> > y ~ 1*x simplifies to y ~ 1
> >
> > Mainly I would have expected y ~ 1:x to simplify to y ~ x and the cross
> > operator to be invariant to order.
> >
> > I have some further surprising cases below that I'd also like to know
> more
> > about but just above will also be great.
> >
> > https://rpubs.com/emitanaka/unexpected-formula-eval
> >
> > Best,
> >
> > Emi
> >
> > *Dr. Emi Tanaka* | Lecturer in Statistics
> >
> > Faculty of Science, School of Mathematics and Statistics
> >
> >
> > Secretary, NSW Branch, Statistical Society of Australia
> > <
> https://www.meetup.com/NSW-Branch-of-the-Statistics-Society-of-Australia/>
> >
> > Social Media Coordinator, Central, International Biometrics Society
> > <https://twitter.com/IBSstats>
> >
> >
> > *THE UNIVERSITY OF SYDNEY*
> > 827, Carslaw F07 | The University of Sydney | NSW | 2006
> > *Phone:* +61 2 9351 3039
> > *Website:* * <http://sydney.edu.au/>*https://emitanaka.github.io/
> > *Twitter: *@statsgen
> >
> > CRICOS 00026A
> > This email plus any attachments to it are confidential.
> > Any unauthorised use is strictly prohibited. If you receive this email in
> > error, please delete it and any attachments. Please think of our
> > environment and only print this e-mail if necessary.
> >
> >         [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > [hidden email] mailing list -- To UNSUBSCRIBE and more, see
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
>
> ______________________________________________
> [hidden email] mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

        [[alternative HTML version deleted]]

______________________________________________
[hidden email] mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.